Vascular edema (angioedema) is a localized edema that occurs in loose subcutaneous tissues or mucous membranes, categorized into acquired and hereditary types, with the latter being rare.

bubble_chart Etiology

Acquired angioedema is often associated with other atopic diseases. Its pathogenesis is similar to urticaria and can be triggered by drugs, food, inhalants, and physical factors. Hereditary angioedema is an autosomal dominant genetic disorder. Patients lack the serum A2 globulin inhibitor of C1 esterase in their serum, or about 15% have normal levels but impaired function. Due to factors such as trauma, intense exercise, or emotional stress, excessive activation of C1 occurs, subsequently activating C4 and C2 and releasing kinins. With the involvement of plasmin, kinins increase vascular permeability and cause mast cells to release histamine, leading to vascular edema. During an attack, both C4 and C2 levels decrease, while C4 remains low during remission. The C1 level is normal in this condition, which helps differentiate it from acquired angioedema.

bubble_chart Clinical Manifestations

It mainly occurs in loose tissues such as the eyelid, lips, external genitalia, hands, feet, etc. It is usually solitary, but occasionally occurs in two or more locations. The lesion is a sudden localized swelling involving subcutaneous tissue, with indistinct borders. The skin color is normal or light red, with a shiny surface and an elastic texture upon touch. It may gradually subside within 1 to 3 days but can also recur in the same area. If it occurs in the laryngeal mucous membrane, it may cause difficulty breathing or even suffocation leading to death.

Hereditary angioedema is a rare autosomal dominant genetic disorder, often occurring more than 10 hours after trauma or impact, and may recur repeatedly. It manifests as non-pruritic angioedema of the skin (commonly seen on the face and limbs). The lesions can range from several centimeters in diameter or occupy one side of a limb, subsiding within 1 to 3 days but prone to recurrence. It may begin in childhood or adolescence and recur until the age of over 40. It can also occur in the mucous membranes of the oral cavity, throat, gastrointestinal tract, and respiratory tract. Patients may die due to sudden laryngeal edema.

The diagnosis is straightforward when sudden, widespread, non-pitting edema occurs and resolves within hours to a day, often affecting the eyelids, lips, tongue, external genitalia, hands, and feet. If the onset is early in life, nearly half of the family members are affected, and early gastrointestinal or respiratory symptoms are present, hereditary angioedema should be considered. A definitive diagnosis can be made if serum levels of esterase inhibitor protein, C4, and C3 are reduced.

bubble_chart Treatment Measures

The treatment of acquired angioedema is the same as that for general urticaria. Hereditary angioedema can be treated with danazol or stanozolol to increase c1INH synthesis, thereby reducing the effect of plasmin on C2 and alleviating symptoms. Alternatively, aminocaproic acid or tranexamic acid can be tried to inhibit plasminogen activity. Before surgery or during acute episodes, in addition to symptomatic treatment, some patients may receive fresh plasma transfusions to supplement C1 esterase inhibitor. However, fresh plasma may also contain complement components, which could trigger symptoms in some patients. If laryngeal edema occurs, preparations should be made for endotracheal intubation or tracheotomy. Generally, antihistamines are not very effective.